linux-kernel - Re: [PATCH 04 of 14] swiotlb: consistently use address_needs

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Message-Id: <20081217113804F.fujita.tomonori@lab.ntt.co.jp>
Date:	Wed, 17 Dec 2008 11:48:41 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	jeremy@...p.org
Cc:	mingo@...e.hu, linux-kernel@...r.kernel.org,
	xen-devel@...ts.xensource.com, x86@...nel.org,
	ian.campbell@...rix.com, jbeulich@...ell.com,
	fujita.tomonori@....ntt.co.jp
Subject: Re: [PATCH 04 of 14] swiotlb: consistently use
 address_needs_mapping	everywhere

On Tue, 16 Dec 2008 12:17:28 -0800
Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> Signed-off-by: Ian Campbell <ian.campbell@...rix.com>
> ---
>  lib/swiotlb.c |   10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)

This patch is wrong.

dma_mask and coherent_dma_mask represent different restrictions.

You can't use coherent_dma_mask for alloc_coherent.


> diff --git a/lib/swiotlb.c b/lib/swiotlb.c
> --- a/lib/swiotlb.c
> +++ b/lib/swiotlb.c
> @@ -465,13 +465,9 @@
>  	dma_addr_t dev_addr;
>  	void *ret;
>  	int order = get_order(size);
> -	u64 dma_mask = DMA_32BIT_MASK;
> -
> -	if (hwdev && hwdev->coherent_dma_mask)
> -		dma_mask = hwdev->coherent_dma_mask;
>  
>  	ret = (void *)__get_free_pages(flags, order);
> -	if (ret && !is_buffer_dma_capable(dma_mask, virt_to_bus(ret), size)) {
> +	if (ret && !address_needs_mapping(hwdev, virt_to_bus(ret), size)) {
>  		/*
>  		 * The allocated memory isn't reachable by the device.
>  		 * Fall back on swiotlb_map_single().
> @@ -495,9 +491,9 @@
>  	dev_addr = virt_to_bus(ret);
>  
>  	/* Confirm address can be DMA'd by device */
> -	if (!is_buffer_dma_capable(dma_mask, dev_addr, size)) {
> +	if (!address_needs_mapping(hwdev, dev_addr, size)) {
>  		printk("hwdev DMA mask = 0x%016Lx, dev_addr = 0x%016Lx\n",
> -		       (unsigned long long)dma_mask,
> +		       (unsigned long long)dma_get_mask(hwdev),
>  		       (unsigned long long)dev_addr);
>  
>  		/* DMA_TO_DEVICE to avoid memcpy in unmap_single */
> 
> 
> --
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